DESCRIPTION (Applicant's abstract verbatim): Computed Tomography (CT) has increasingly become a three-dimensional imaging modality. Spiral CT and more recently multi-slice detector arrays have rapidly advanced the use of CT for 3D applications, such as mapping of tumors for treatment planning and CT angiography studies. Phantoms required for quality assurance of 3D imaging performance, especially low-contrast (LC) resolution, have not kept pace with these advancements. Presently, there are no commercially available low-contrast resolution phantoms that permit measurements for image reconstructions along the z-axis (perpendicular to a traditional CT image slice). Existing 2D LC resolution phantoms, such as the "ATS" phantom, exhibit large variations in object contrast with changes in beam quality. This renders QA measurements less reliable and comparisons between different scanners of questionable value. In this proposal, we will investigate the use of advanced materials technology to create a 3D LC resolution phantom whose measured contrast is independent of beam quality. In Phase I, a prototype phantom will be constructed and its performance measured and compared to existing phantoms. PROPOSED COMMERCIAL APPLICATIONS: The proposed research will lead to a new 3D low-contrast resolution phantom whose contrast is independent of beam quality. The phantom will have immediate commercial use, especially with spiral CT scanners, to allow accurate and reliable measurement of low-contrast resolution in all three spatial dimensions. Resolution measurements in the z-axis direction are not possible with existing phantoms. The beam quality independence of the contrast will allow meaningful comparison of the resolution performance between different CT scanners, and will remove possible inaccuracies in QA of a single scanner due to changes in kVp or filtration. We estimate the potential sales of this phantom to exceed $1 M per year.